1. Technical Field of the Invention
The present invention relates to a fin-and-tube-type heat exchanger, in the tube of which an inner fin is provided. The fin-and-tube-type heat exchanger of the present invention is preferably used for an inter-cooler for cooling suction air of an internal combustion engine and can also be used for a condenser for emitting the heat of a thermal medium of an air conditioner.
2. Description of the Related Art
In a conventional tube of a heat exchanger into which an inner fin is incorporated, a set of plates are engaged with each other so that an inner fin can be interposed between them, as described in the official gazette of JP-A-2003-28586 (FIGS. 6 and 8). In the case where the tube is divided into two pieces as described above, at the time of forming the tube, it is easy to incorporate the fin into the tube.
However, in the case where the tube is divided into two pieces, the following problems may be encountered. In a portion in which the plates are engaged with each other, on an outer wall face of the tube, a step portion is formed which corresponds to the wall thickness of the plate arranged outside. When this step portion is formed, at the time of inserting the tube onto a header plate, a gap is formed between the outer wall face of the tube and the opening edge of the opening portion of the header plate. Accordingly, at the time of brazing, a brazing failure may occur.
As a means for solving the above problem, a tube has been proposed, and the structure disclosed, in FIG. 6 of the official gazette of JP-A-2003-28586. That is, a tube, the cross-section of which is substantially a flat rectangle, is composed in such a manner that a first plate, the lateral cross-section of which is substantially a C-shape, and a second plate, the lateral cross-section of which is also substantially a C-shape, are opposed and engaged with each other. In a portion in which both plates are engaged mutually, the first plate is located outside the second plate. An edge portion of the first plate is formed into a shape which lies along a bent portion of the second plate. Due to the above structure, the outer wall face of the tube is composed of continuous face.
The present inventors have investigated application of the tube described above to a fin-and-tube-type heat exchanger. FIG. 13 is a sectional view showing a tube and an outer fin of the heat exchanger which the present inventors investigated. In this connection, FIG. 13 corresponds to a sectional view taken on line III-III in FIG. 1.
As shown in FIG. 13, the tube 2 has a lateral sectional shape formed into substantially a flat rectangle. The first plate 6, the lateral cross section of which is formed into a substantial C-shape, and the second plate 7, the lateral cross section of which is also formed into a substantial C-shape, are opposed and engaged with each other. In a portion in which both plates 6, 7 are engaged mutually, in order to make an outer wall face of the tube 2 to be continuous face, an edge portion 6a of the first plate 6 composing the outer wall face is located in a bent portion 7b of the second plate 7 with respect to the entire tube 2, and the edge portion 6a of the first plate 6 is formed into a shape which lies along the bent portion 7b of the second plate 7.
In the tube 2, an inner fin 5 is arranged. On an outer wall face of the tube 2, an outer fin 3 is provided. This outer fin 3 is arranged only on a main surface 2a which is one of the surfaces including the main surface 2a shown in FIG. 13 composing a long side of the substantial rectangle on the lateral cross section of the tube and the side 2b shown in FIG. 13 composing a short side of the substantial rectangle. In this connection, in FIG. 13, an outer fin arranged on the main surface 2a on the lower side of the drawing is omitted.
Even in this case, the outer wall face of the tube 2 is substantially composed of continuous face. Therefore, it is possible to solve the problem explained in the item of the background art.
However, when the tube 2 is composed as described above, the following problems may be encountered. At the time of manufacturing the heat exchanger, when the first plate 6, the second plate 7, the inner fin 5 and the outer fin 3 are simultaneously brazed mutually in a furnace, in the case where a failure is caused in brazing of the first and the second plate, it is difficult to conduct repairing. That is, when a brazing failure may occur, repairing is usually conducted in such a manner that a brazing filler metal is arranged in a portion in which the failure of brazing is caused and a torch brazing is conducted in which the defective portion is heated with a burner. However, since the edge portion 6a of the first plate 6 is located in the bent portion 7b of the second plate 7 and the edge portion 6a of the first plate 6 is obstructed by the outer fin 3, it is impossible to arrange the brazing filler metal in the neighborhood of the edge portion 6a of the first plate 6. When repairing is forcibly conducted, the outer fin 3 is melted by the burner. Therefore, it is difficult to conduct repairing.
The above problems are caused not only in the tube composed in such a manner that the tube is formed out of two divided plates but also in the tube composed in such a manner that the tube is formed out of one plate and both edge portions of the one plate, which are opposed mutually, are engaged mutually so that the tube can be formed.